Electrical circuit arrangement for complex wave generators



D. J. LESLIE July 3, 1962 ELECTRICAL CIRCUIT ARRANGEMENT FOR COMPLEX WAVE GENERATORS Filed Jan. 29, 1959 N m QMNQWO Bax 040 d IE5; /E

IN V EN TOR.

JV Mu w I flrraewsys United States Patent 3,041,910 ELECTRICAL CIRCUIT ARRANGEMENT FOR COMPLEX 'WAVE GENERATORS Donald J. Leslie, Electro Music, 313 S. Fair Oaks Ave, Pasadena,-Calif. Filed Jan. 29, 1959, Ser. No. 789,968 3 Claims. -(Cl. 84-122) This invention relates to musical instruments, particularly electronic instruments which generate impulses corresponding to musical tones.

The significant problem in connection with electronic instruments is that upon electrical mixture, certain beat effects are produced due either to mistuning of generators or the inherent characteristics of the tempered scale.

Thus, for example, if the impulse for A4440 cycles per second) contains a second harmonic at 880.00 c.p.s., thissecond'harmonic may beat with the fundamental of the impulse for A Thus, the generator for A may be slightly mistuned so that the fundamental impulse is at a frequency of, say, 881.00 c.p.s. Periodically, the two components will, in the electrical circuit, reinforce and buck each other, and a beat elfect will be perceived. Periodic reinforcement and bucking occurs at the rate corresponding to the mistuning of the respective components, in this instance at about one cycle per second.

Impulses for notes in fourth or fifth musical interval relationship with respect to each other also create the possibility of beat effects even though the impulses are perfectly tuned. Thus, for example, the impulse for A, may contain a substantial third harmonic at 1320.00 c.p.s. If an impulse rich in second harmonic for the note E (five musical intervals above A is simultaneously sounded, a component of twice 659.26 c.p.s. or 1318.52 c.p.s. will be created. Thus, the third harmonic of A creates the possibility of a beat effect with the second harmonic of E and even though these notes are precisely tuned in accordance with the tempered scale.

Similarly, if an impulse rich in fourth harmonic exists simultaneously with an impulse for a note in fourth interval relationship therewith, a possibility of heating is also created. For example, the fourth harmonic of A 1760.00 c.p.s., may beat with the third harmonic of B 1761.99 c.p .s.

While there are other conditions of harmonics or fundamentals creating the possibility of beat effects, I have noted that the most objectionable beats result from the 3,041,910. Patented July 3, 1962 4; invention. 'For this purpose, there is shown a form in the drawings accompanying and forming part of the present specification. This form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

The single figure diagrammatically illustrates the system incorporating the present invention.

In FIG. 1, a set of generators 10 is illustrated which, for purposes of discussion only, is made up of a plurality of octave sets 1, 2, 3, 4, 5 and 6 designated by corresponding blocks.

Available in association with the the generators are two types of outputs, one, as at E for the octave group 1 at which only even harmonics are present. Another terminal 0 provides only the fundamental in odd harmonies. These diiferent'outputs may be made available in a number of various ways, for example, by transformer arrangements, non-linear circuit elements, bucking circuits, and the like; or they may be made available by different pickups from tone Wheels or the like. Terminals E E E E and E; for even harmonics and O O O O and 0 for the fundamental and odd harmonics are provided for the octave generator groups 1, 2, 3, 4, 5 and 6. Corresponding outputs are connected together; for example, a lead 13 connects with like E terminals, and a lead 14 connects with corresponding 0' terminals.

An amplifier 15 and a transducer or speaker 16 cooperate with the bus connection or output lead 13, and a separate amplifier 17 and speaker 18 cooperate with the other outputs via the lead 14. Suitable key switches (not simultaneous existence of odd harmonics with even harmonies, the fundamental being considered the first harmonic for purposes of this discussion. An object of this invention is toprovide a novel system whereby beat effects due both to mistuning as well as to inherent characteristics of the tempered scale are at the same time minimized, and by providing only two channels.

To implement the invention, electrical isolation of incompatible frequencies is achieved by grouping generator output into two sections. One section contains the fundamental and all odd harmonics; the second section contains only the even harmonics. Both sections have their separate amplifiers and speakers, and electrical intermixture is avoided. When the sounds emanate from the respective speakers of the sections that are necessarily spaced from each other, the beat effect is minimized, the acoustic mixing being random rather than regular, Hence, the regular periodic reinforcement and bucking does not occur to the extent that it would if the impulses 1 shown) may be interposed either in the excitation or input circuit to the various generators or in the output circuit, and as diagrammatically indicated for example in FIGS. 1 and 2 respectively of my prior Patent No. 2,596,- 258, issued May 13, 1952. Since this invention requires the use of two output connections 13 and 14, key switches are most advantageously placed in the input circuits.

Electrical intermixture of even and odd harmonics (considering the fundamental as the first harmonic) is thus precluded by the present segregation system, and beating accordingly is substantially minimized. For example, the second harmonic of A, will exist at the tap E, by virtue of the fact that it is an even harmonic. This will be translated into sound by virtue of the channel including the amplifier 15 and speaker 16. There will be no possibility of beating occurring with respect to the fundamental of A for the reason that the fundamental of A exists at the tap O and is translated by the other channel including the amplifier 17 and the speaker 18. Similarly, odd and evenharmonics in notes of fourth or fifth musical interval relationship exist in the respective channels and beating due to this cause is likewise minimized.

The inventor claims:

1. In an electronic organ system or the like: a set of generators for producing impulses corresponding to musical notes in a range of several octaves; means providing a pair of separate electrical channels in one of which substantially only fundamental impulses and all odd harmonies from all of the generators exist, and in the other of which substantially only even harmonics from all of the generators exits; and separate transducers for the respective channels.

2. In an electronic organ system or the like: a set of generators for producing impulsescorresponding to musical notes in a range of several octaves; each generator having a first output at which only the fundamental and odd harmonics exist and a second output at which only the even harmonics exist; a pair of separate electrical channels each including transducer means; first coupling means between corresponding first outputs of the generators and one of said channels; and second coupling means between corresponding second outputs of the generators and the other of said channels.

nections; and means connecting the said second outputs substantially exclusively to the other bus connection.

References Cited in the file of this patent UNITED STATES PATENTS 1,592,937 Jammer July 20, 1926 1,823,724 Carlson Sept. 15, 1931 1,958,866 Severy May 15, 1934 2,562,908 Hanert -c Aug. 7, 1951 10 2,596,258 Leslie May 13, 1952 OTHER REFERENCES Fox Electronic Eng, A Waveform Synthesizer, September 1955, pages 374-678. 

